Radiation Beam Source Device

Abstract

For optical data storage applications, for example, for holographic storage applications, a radiation beam ( 12 ) with a flat intensity profile is needed. The radiation source device ( 1 ) of the invention comprises a beam shaper element ( 5 ) and a collimating element ( 7 ) between a semiconductor laser ( 3 ) and an output coupler ( 9 ) and provides such a radiation beam ( 12 ) with an increased efficiency. An external resonator is thereby provided. Further, a relatively fast tuning of the wavelength of the output radiation beam ( 12 ) can be provided.

1 . Radiation source device ( 1 ) for an optical storage system, which radiation source device comprises:
 at least a radiation emitting element ( 2 ) for emitting a radiation beam,   at least a beam shaper element ( 5 ) for shaping the radiation beam emitted from said radiation emitting element to an at least nearly circular radiation beam,   at least a collimating element ( 7 ), wherein said circular radiation beam from said beam shaper element is input to said collimating element and said collimating element is arranged to output a radiation beam with an at least nearly flat intensity profile, and   at least an output coupler ( 9 ) which is arranged to partially reflect said radiation beam from said collimating element at least indirectly back to said radiation emitting element and to output a output radiation beam ( 12 ).   
     
     
         2 . Radiation source device according to  claim 1 , characterized in that said radiation emitting element ( 2 ) comprises a semiconductor laser ( 3 ) emitting an elliptical radiation beam. 
     
     
         3 . Radiation source device according to  claim 2 , characterized in that said beam shaper element ( 5 ) shapes said elliptical radiation beam output from said radiation emitting element to said circular radiation beam. 
     
     
         4 . Radiation source device according to  claim 1 , characterized in that said collimating element ( 7 ) comprises at least a collimating lens. 
     
     
         5 . Radiation source device according to  claim 1 , characterized in that said collimating element ( 7 ) is arranged to output a radiation beam having a rim intensity that is at least slightly greater than or equal to the center intensity of said radiation beam. 
     
     
         6 . Radiation source device according to  claim 1 , characterized in that said output coupler ( 9 ) comprises at least a reflecting element ( 10 ,  25 ,  35 ). 
     
     
         7 . Radiation source device according to  claim 6 , characterized in that said reflecting element is a bragg reflector ( 10 ). 
     
     
         8 . Radiation source device according to  claim 6 , characterized in that said reflecting element is a refractive grating. 
     
     
         9 . Radiation source device according to  claim 8 , characterized in that said reflecting element is arranged to be movable to change an angle of incidence of said radiation beam on said reflecting element. 
     
     
         10 . Radiation source device according to  claim 9 , characterized in that said reflecting element is movable by a piezo-element ( 29 ) to control the wavelength of said output radiation beam. 
     
     
         11 . Radiation source device according to  claim 1 , characterized in that said output coupler comprises a mirror element ( 40 ), wherein said mirror element is arranged to reflect an incident radiation beam at a changeable reflecting area, and said radiation source device comprises a control unit ( 45 ) to control the position of said reflecting area on the mirror element ( 40 ) to set the wavelength of said radiation beam output. 
     
     
         12 . Radiation source device according to  claim 11 , characterized by a further reflecting element, wherein said further reflecting element is arranged so that a surface of said further reflecting element ( 35 ) is at least at most parallel to a surface of said reflecting element. 
     
     
         13 . Radiation source device according to  claim 11 , characterized by at least a focusing lens ( 39 ) for focusing the radiation beam on the mirror element. 
     
     
         14 . Optical data storage device ( 50 ) for optical data storage comprising a radiation source device according to  claim 1 .